A request to fly a seriously ill asylum seeker off Manus Island was not acted on for more than 24 hours because of delays, including the man's lack of a visa to enter the PNG mainland.

Hamid Kehazaei, whose skin infection had turned into potentially fatal septicaemia, was later taken by air ambulance to hospital at Port Moresby and then on to Brisbane where he was pronounced brain dead and his life support switched off.

Documents obtained by the ABC show staff working for government contractor International Health and Medical Services (IHMS) warned that all antibiotic treatment at the Manus camp had been exhausted and Mr Kehazaei's condition was deteriorating.

A "recommendation for medical movement", written on the morning of August 25, recommended "urgent transfer by commercial carrier, with a medical escort and ground transfer from airport to hospital in Port Moresby".

"There is a commercial flight leaving Manus to Port Moresby today at 17:30," Dr Yliana Dennett wrote at 11:30am.

"The medical officer Dr Richard McGrath is already booked on this flight and can act as a medical escort if approved."

Mr Kehazaei, a 24-year-old Iranian, had been diagnosed with severe septicaemia in his leg spreading to the groin, which medical staff warned in their request for a hospital transfer could lead to a "life-threatening systemic infection".

According to the documents, Mr Kehazaei had presented to the detention centre clinic two days earlier with an "infected blister in the left shin and intermittent fever".

The condition of Mr Kehazaei, also known by his identification number GDD059, had "worsened considerably" with staff warning that the "infectious process can spread quickly and if not treated appropriately can develop into a life or limb-threatening situation".

But the seriously ill man was not flown off the island until the afternoon of the following day.

"Plans to transfer patient to [Port Moresby] never came to fruition due to delays/visa requirements, so [patient] spent another night here," detention centre medical staff wrote on the morning of August 26.

"Patient remains very unwell despite all of our efforts," staff wrote at 10:11am.

It was not until 4:15pm – more than 24 hours after it was recommended that he be flown to Port Moresby – that Mr Kehazaei made it to the Pacific International Hospital in the PNG capital.

He was flown from Manus not on a commercial flight but in an air ambulance, the cost of which had been estimated at $51,000, according to the documents obtained by the ABC.

The documents also reveal that once Mr Kehazaei made it to hospital in Port Moresby his condition deteriorated further and he went into cardiac arrest.

He died at the Mater Hospital on September 5.

The documents do not reveal whether a visa was obtained for Mr Kehazaei to enter PNG.

Bureaucratic process often brings delays, doctor says

Dr Peter Young, a former head of mental health services in immigration detention for IHMS, told the ABC that reports such as the one recommending Mr Kehazaei's medical evacuation would have been forwarded immediately to the Immigration Department.

But Dr Young said there were often delays as a result.

"The processes are that those type of recommendations are made and put through to the relevant decision-makers in the department fairly quickly, certainly in my experience when I was there," he said.

"The difficulty then becomes what happens through the internal processes in the department and the minister's office.

"And often they come back with questions and further questions and then all of that just delays the process.

"The department has been very critical of IHMS at different times in these sort of circumstances, and their feedback has been consistently that IHMS has been too ready to refer people for treatment offsite.

"It's come up in lots of discussions and feedback from the department."

International Health and Medical Services declined to comment to the ABC, referring questions to Immigration Minister Scott Morrison's office.

Mr Morrison also declined to comment, saying the case was a matter for the Queensland Coroner.